Ropinirole is a compound represented by the following formula (1) and is also referred to as 4-[2-(dipropylamino)ethyl]-2-indolinone. Ropinirole is known as a dopamine D2 receptor agonist and an oral administration formulation containing ropinirole hydrochloride is in particular effective in treating diseases such as Parkinson's disease and restless legs syndrome.

On the other hand, ropinirole may cause side effects such as somnolence and narcolepsy in response to the increase in a body drug concentration, and the development of a transdermal absorption formulation allowing the administration at a constant rate has been attempted (Patent Literature 1 to 7).